Curing and thermal properties of a microwave radiation-curable epoxy/latent catalyst system

In this work, the microwave curing of an epoxy resin, the diglycidyl ether of bisphenol A (DGEBA), was investigated in terms of its thermal and dynamic mechanical properties. Benzylquinoxalinium hexa-fluoroantimonate (BQH) was used as a latent catalyst in this system. The cure behavior of the DGEBA/BQH system was monitored by measuring near-infrared (NIR) spectra before and after curing; the highest conversion (α) occurred at a radiation time of 15 min. The thermal stabilities, characterized from the integral procedural decomposition temperature (IPDT), were increased until the radiation time reached 15 min and then slowly decreased upon increasing the radiation time further. The values of the crosslinking density (ρ) and T_g obtained from dynamic mechanical analysis (DMA) showed behavior similar to that of the values of α and the thermal stabilities, probably because of the increased crosslinking density of the system developed by intermolecular interactions in the macromolecular chains.